1. The Field of the Invention
The present invention relates generally to compositions for manufacturing cellular articles from highly inorganically filled materials having a starch-based binder. More particularly, the present invention relates to economically mass-produced, environmentally superior containers and other articles prepared by combining particle packed inorganic fillers and a starch-based binder with a solvent and other desired admixtures to form a mixture having a controlled viscosity. The mixture is positioned between opposing molds where the temperature and pressure are elevated to rapidly form the mixture into a form-stable article having a selectively designed cellular structural matrix. The components for the mixture and the processing parameters can be selected to produce articles that have desired properties of, e.g., thickness, stiffness, flexibility, insulation, toughness, product stability, and strength. The resulting articles can also be produced less expensively and more environmentally safe than articles made from conventional materials, e.g., paper, plastic, polystyrene foam, glass, or metal.
2. The Relevant Technology
A. Articles of Manufacture
Materials such as paper, paperboard, plastic, polystyrene, and even metals are presently used in enormous quantity in the manufacture of articles such as containers, separators, dividers, lids, tops, cans, and other packaging materials. Advanced processing and packaging techniques presently allow an enormous variety of liquid and solid goods to be stored, packaged, or shipped in such packaging materials while being protected from harmful elements.
Containers and other packaging materials protect goods from environmental influences and distribution damage, particularly from chemical and physical influences. Packaging helps protect an enormous variety of goods from gases, moisture, light, microorganisms, vermin, physical shock, crushing forces, vibration, leaking, or spilling. Some packaging materials also provide a medium for the dissemination of information to the consumer, such as the origin of manufacture, contents, advertising, instructions, brand identification, and pricing.
Typically, most containers and other packaging materials (including disposable containers) are made from paper, paperboard, plastic, polystyrene, glass, or metal materials. Each year, over 100 billion aluminum cans, billions of glass bottles, and thousands of tons of paper and plastic are used in storing and dispensing soft drinks, juices, processed foods, grains, beer, and other products. Outside of the food and beverage industry, packaging containers (and especially disposable containers) made from such materials are ubiquitous. Paper-based articles made primarily from tree derived wood pulp are also manufactured each year in enormous quantities. In the United States alone, approximately 5.5 million tons of paper are consumed each year for packaging purposes, which represents only about 15% of the total annual domestic paper production.
B. The Impact of Paper, Plastic, Glass and Metal
Recently, there has been a debate as to which of the conventional materials (e.g., paper, paperboard, plastic, polystyrene, glass, or metal) is most damaging to the environment. Consciousness-raising organizations have convinced many people to substitute one material for another in order to be more environmentally "correct." The debate often misses the point that each of these materials has its own unique environmental weaknesses. One material may appear superior to another when viewed in light of a particular environmental problem, while ignoring different, often larger, problems associated with the supposedly preferred material.
Polystyrene products, particularly containers and other packaging materials, have more recently attracted the ire of environmental groups. While polystyrene itself is a relatively inert substance, its manufacture involves the use of a variety of hazardous chemicals and starting materials. Unpolymerized styrene is very reactive, and therefore presents a health problem to those who must handle it. Because styrene is manufactured from benzene (a known mutagen and a probable carcinogen), residual quantities of benzene can be found in styrene.
More potentially damaging has been the use of chlorofluorocarbons (or "CFCs") in the manufacture of "blown" or "expanded" polystyrene products. This is because CFCs have been linked to the destruction of the ozone layer. In the manufacture of foams, including blown polystyrene, CFCs (which are highly volatile liquids) have been used to "expand" or "blow" the polystyrene into a foamed material, which is then molded into the form of cups, plates, trays, boxes, "clam-shell" containers, spacers, or packaging materials. Even the substitution of less "environmentally damaging" blowing agents (e.g., HCFCs, pentanes, and CO.sub.2 with hydrocarbon combinations) are still significantly harmful and their elimination would be beneficial.
As a result, there has been widespread pressure for companies to stop using polystyrene products in favor of more environmentally safe materials. Some environmental groups have favored a temporary return to the use of more "natural" products, such as paper or other products made from wood pulp, which are believed to be biodegradable. Nevertheless, other environmental groups have taken the opposite view in order to minimize the cutting of trees and depletion of forests.
Although paper products are ostensibly biodegradable and have not been linked to the destruction of the ozone layer, recent studies have shown that the manufacture of paper probably more strongly impacts the environment than does the manufacture of polystyrene. In fact, the wood pulp and paper industry has been identified as one of the five top polluters in the United States. For instance, products made from paper require ten times as much steam, fourteen to twenty times the electricity, and twice as much cooling water as compared to an equivalent polystyrene product. Various studies have shown that the effluent from paper manufacturing contains ten to one hundred times the amount of contaminants produced in the manufacture of polystyrene foam.
In addition, a by-product of paper manufacturing is that the environment is impacted by dioxin, a harmful toxin. Dioxin, or more accurately, 2,3,7.8-tetrachlorodibenzo[b,e][1,4]-dioxin, is a highly toxic contaminant, and is extremely dangerous, even in very low quantities. Toxic effects of dioxin in animals and humans include anorexia, severe weight loss, hepatoxicity, hematoporphyrin, vascular lesions, chloracne, gastric ulcers, porphyrinuria, porphyria, cutanea tarda, and premature death. Most experts in the field believe that dioxin is a carcinogen.
Another drawback of the manufacture of paper and paperboard is the relatively large amount of energy that is required to produce paper. This includes the energy required to process wood pulp to the point that the fibers are sufficiently delignified and frayed that they are essentially self-binding under the principles of web physics. In addition, a large amount of energy is required in order to remove the water within conventional paper slurries, which contain water in an amount of up to about 99.5% by volume. Because so much water must be removed from paper slurries, it is necessary to literally suck water out of the slurry even before the drying process is begun. Moreover, much of the water that is sucked out during the dewatering processes is usually discarded into the environment.
The manufacturing processes of forming metal sheets into containers (particularly cans made of aluminum and tin), blowing glass bottles, and shaping ceramic containers utilize high amounts of energy because of the necessity to melt and then separately work and shape the raw metal into an intermediate or final product. These high energy and processing requirements not only utilize valuable energy resources, but they also result in significant air. water, and heat pollution to the environment. While glass can be recycled, that portion that ends up in landfills is essentially non-degradable. Broken glass shards are very dangerous and can persist for years.
Some of these pollution problems are being addressed; however, the result is the use of more energy, as well as the significant addition to the capital requirements for the manufacturing facilities. Further, while significant efforts have been expended in recycling programs, only a portion of the raw material needs come from recycling--most of the raw materials still come from nonrenewable resources.
Even paper or paperboard, believed by many to be biodegradable, can persist for years, even decades, within landfills where they are shielded from air, light, and water--all of which are required for normal biodegradation activities. There are reports of telephone books and newspapers having been lifted from garbage dumps that had been buried for decades. This longevity of paper is further complicated since it is common to treat, coat, or impregnate paper with various protective materials that further slow or prevent degradation.
Another problem with paper, paperboard, polystyrene, and plastic is that each of these requires relatively expensive organic starting materials, some of which are nonrenewable, such as the use of petroleum in the manufacture of polystyrene and plastic. Although trees used in making paper and paperboard are renewable in the strict sense of the word, their large land requirements and rapid depletion in certain areas of the world undermines this notion. Hence, the use of huge amounts of essentially nonrenewable starting materials in making articles therefrom cannot be sustained and is unwise from a long term perspective. Furthermore, the processes used to make the packaging stock raw materials (such as paper pulp, styrene, or metal sheets) are very energy intensive, cause major amounts of water and air pollution, and require significant capital requirements.
In light of the foregoing, the debate should not be directed to which of these materials is more or less harmful to the environment, but rather toward asking: Can we discover or develop an alternative material which will solve most, if not all, of the various environmental problems associated with each of these presently used materials?
C. Alternative Materials
Due to the more recent awareness of the tremendous environmental impacts of using paper, paperboard, plastic, polystyrene, and metals for a variety of single-use, mainly disposable, articles such as containers and other packaging materials made therefrom (not to mention the ever mounting political pressures), there has been an acute need (long since recognized by those skilled in the art) to find environmentally sound substitute materials.
One alternative has been to make the desired articles and containers out of baked, edible sheets, e.g., waffles or pancakes. Although edible sheets can be made into trays, cones, and cups which are easily decomposed, they pose a number of limitations. Edible sheets are primarily made from a mixture of water, flour, and a rising agent. The mixture is baked between heated molds into its desired shape. Fats or oils are added to the mixture to permit removal of the sheet from the baking mold. Oxidation of these fats cause the edible sheets to go rancid. From a mechanical standpoint, the resulting edible sheets are very brittle and far too fragile to replace most articles made from conventional materials. Furthermore, edible sheets are overly sensitive to moisture and can easily mold or decompose prior to or during their intended use.
Attempts have also been made to make articles using organic binders. For example, articles have been made from mixtures of starch, water, and a mold-releasing agent. The starch-based mixtures were baked between heated molds until the starch gelated and set in the desired shape for the articles. The resulting products, however, were found to be cost prohibitive. Slow processing times, expensive equipment, and the relatively high cost of starch compared to conventional materials made the articles more expensive than conventional articles. Although inorganic fillers have been added to starch-based mixtures in an attempt to cut material cost, mixtures containing any significant portion of fillers were unable to produce structurally stable articles that had functional mechanical properties.
Furthermore, the starch-based articles were found to be very fragile and brittle, giving them limited use. To improve flexibility, the articles were placed in a humidity chamber where the moisture was absorbed by the starch to soften the articles. The moisture absorption, however, took several minutes, significantly slowing down the manufacturing process. Furthermore, an additional time-consuming step of applying a coating to the article was required to prevent the moisture from escaping from the article once the article was finished. Attempts at producing organic-based articles have also failed to consistently produce articles that have a smooth, uniform surface. To disguise the surface defects, the articles have usually been made with a waffled surface.
Industry has repeatedly sought to develop inorganically filled materials for the production of disposable articles that are mass-produced and used in large quantities. Inorganic materials such as clay, natural minerals, and stone are easily accessed, non-depletable, inexpensive, and environmentally inert. In spite of economic and environmental pressures, extensive research, and the associated long-felt need, the technology simply has not existed for the economic and feasible production of highly inorganically filled materials which could be substituted for paper, paperboard, plastic, polystyrene, metal, or other organic-based containers and other articles.
Significant attempts have been made over many years to fill conventional paper with inorganic materials, such as kaolin and/or calcium carbonate, although there is a limit (about 20-35% by volume) to the amount of inorganics that can be incorporated into paper products. In addition, there have been attempts to fill certain plastic packaging materials with clay in order to increase the breathability of the product and improve the ability of the packaging material to keep fruits or vegetables stored therein fresh. In addition, inorganic materials are routinely added to adhesives and coatings in order to impart certain properties of color or texture to the final product. Nevertheless, inorganic materials only comprise a small fraction of the overall material used to make packaging materials or other articles, rather than making up the majority of the material mass. Attempts to increase the amount of inorganic filler in a polymer matrix have had significant adverse affects on the rheology and properties of the binding system, e.g., loss of strength, increased brittleness, etc.
In light of the fact that inorganic materials are typically the most economical and ecological material, what is needed are highly inorganically filled materials that can replace paper, paperboard, plastic, polystyrene, or metal materials as the material of choice for producing containers and articles currently made therefrom. What is further needed is an inexpensive, environmentally safe, organic material that, in relatively small quantities, acts as a satisfactory binder for the inorganic material.
It would be a further improvement in the art to form the highly inorganically filled mixture having an organic binder into containers and other articles currently made from paper, paperboard, polystyrene, metal, plastic, or other organic materials.
It would be a significant improvement in the art if such mixtures yielded highly inorganically filled articles which had properties similar to or superior to paper, paperboard, polystyrene, plastic, or metal materials.
It would yet be an improvement in the art if the above containers and articles could be manufactured with or without being placed in a humidity chamber to obtain the desired flexibility.
It would be still another advantage in the art if the above articles could be formed without the need to subsequently apply a coating thereto.
It would be an improvement in the art if the above articles and containers could be formed having a smoother, more uniform surface with fewer defects.
It would also be a tremendous improvement in the art if such articles could be formed using existing manufacturing equipment and techniques presently used to form such articles from paper, paperboard, polystyrene, plastic, or other organic materials.
It would be another improvement in the art if such compositions for manufacturing articles did not result in the generation of wastes involved in the manufacture of paper, paperboard, plastic, polystyrene, or metal materials.
It would be yet an advancement in the art if the compositions contained less water which had to be removed during the manufacturing process (as compared to paper manufacturing) in order to shorten the processing time and reduce the initial equipment capital investment.
In addition, it would be a significant improvement in the art if such articles were readily degradable into substances which are commonly found in the earth.
From a practical point of view, it would be a significant improvement if such materials made possible the manufacture of containers and other articles at a cost that was comparable or even superior to existing methods of manufacturing containers or other articles from paper, paperboard, plastic, polystyrene, or metal. Specifically, it would be desirable to reduce the energy requirements, conserve valuable natural resources, and reduce the initial capital investment for making articles having the desirable characteristics of conventional materials such as paper, metals, polystyrene, plastic, or other organic materials.
From a manufacturing perspective, it would be a significant advancement in the art of shaping highly inorganically filled materials to provide compositions for mass-producing highly inorganically filled articles which could rapidly be formed and ready for use within a matter of minutes from the beginning of the manufacturing process.
It would also be a tremendous advancement in the art to provide compositions which allow for the production of highly inorganically filled materials having greater flexibility, flexural strength, toughness, moldability, mass-producibility, product stability, and lower environmental impact compared to conventional materials having a high content of inorganic filler.
Such compositions and articles are disclosed and claimed herein.